1. Field of Invention
The present invention relates to an EGR cooler; and, particularly, to an EGR cooler and an EGR cooler device using the same capable of relieving a thermal load generated due to hot exhaust gas and simultaneously reducing costs by a decrease in number of EGR tubes via cooling performance enhancement by placing a pre-cooler in a central space of the EGR cooler such that the pre-cooler is surrounded with cooling water circulating in an inner space of the EGR cooler.
2. Description of Related Art
In general, an Exhaust Gas Recirculation (EGR) cooler is included in an EGR system which serves to decrease harmful ingredients such as CO, HC, and NOx (nitrogen oxides) contained in exhaust gas.
Such an EGR cooler serves to convert hot exhaust gas into EGR gas as cold exhaust gas having a relatively lower temperature using cooling water.
As an example, the EGR cooler introduces exhaust gas having a high temperature of about 600° C. and performs heat-exchange between the exhaust gas and the cooling water, thereby allowing the exhaust gas to be converted into EGR gas having a low temperature of about 140° C.
However, if the temperature of the exhaust gas is increased, a generation amount of NOx is gradually increased. Accordingly, there is a need for a measure to more efficiently lower the temperature of the exhaust gas in the EGR cooler. A pre-cooler may be exemplified as the EGR cooler having improved performance so as to more efficiently lower the temperature of the hot exhaust gas.
This pre-cooler allows the introduced hot exhaust gas to be formed at a temperature lower by two levels than that thereof using the cooling water, thereby enabling the temperature of the EGR gas emitted from the EGR cooler to be converted into a much lower temperature.
However, the pre-cooler is configured by an aluminum body and integrated into the EGR cooler, so that the EGR cooler has a structural limit due to the pre-cooler.
As an example of such influence, when the pre-cooler has insufficient cooling performance, the EGR cooler is subject to a thermal load by introduction of the hot exhaust gas into the pre-cooler and the thermal load of the EGR cooler generates a crack in the EGR cooler.
As another example of such influence, there is a case in which an EGR valve connected to the EGR cooler is subject to a thermal load by the hot exhaust gas emitted from the pre-cooler. In this case, after the exhaust gas emitted from the pre-cooler is first introduced into the EGR valve, the exhaust gas is discharged from the EGR valve and then introduced into the EGR cooler again. Consequently, the thermal load due to the hot exhaust gas emitted from the pre-cooler increases damage to an electronic control circuit of the EGR valve and wear of a valve rotation portion.
Particularly, if the temperature of the exhaust gas emitted from the pre-cooler exceeds a critical temperature of the EGR valve, damage due to the thermal load cannot help but increase in the EGR valve.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.